Hello!

My first thought is the throttle body. Antifreeze goes through it to prevent it from freezing, and so it may be possible that there's a leak in there.

You mention you changed the thermostat+housing, have you done the rest of your regular maintenance? If you look in my garage in my profile, you'll see the bare minimum you should have done for your car's age (I'd do more with mine, but working minimum wage only goes so far at a time!)